As a substrate for fabrication of a semiconductor integrated circuit, a silicon wafer fabricated by a CZ (Czochralski) method is mainly used. In the most advance imaging element (a CCD, a CMOS image sensor, or the like) in recent years, a dark current failure called a white flaw occurs. It is said that the white flaw occurs due to presence of any defect which forms a deep level. Specifically, there is a metal impurity. It is well known that presence of the metal impurity in a device active region causes a white flaw failure.
As any other known defect which forms a deep level, there are a CiCs defect, a CiOi defect, and the like. The CiCs defect is a complex of interstitial carbon and lattice position carbon, the CiOi defect is a complex of interstitial carbon and interstitial oxygen, and they can be a cause of a white flaw failure since they form a deep level.